Papular polymorphic light eruption: an immunoperoxidase study using monoclonal antibodies.

Biopsy specimens of papules taken from eight patients with polymorphic light eruption were examined by immunoperoxidase techniques employing monoclonal antibodies. In each case, most infiltrating mononuclear cells were T cells. The majority of T cells were T8-positive (cytotoxic/suppressor) in four cases and T4-positive (helper/inducer) in two. In two cases, approximately equal numbers of both T cell subsets were present. In only three cases were rare B cells identified by their reactivity with anti-IgM antibody. MI-positive mononuclear cells (macrophages) represented less than 5% of cells infiltrating the dermis. In five subjects, anti-T6 antibody stained increased numbers of dermal mononuclear cells considered to be Langerhans/indeterminate cells. The pathogenesis of papular polymorphic light eruption may involve injury to upper dermal venules mediated by T cells and Langerhans/indeterminate cells.